The related applications describe and claim a power supply controller, and various features thereof, which can be used for controlling a plurality of isolating power supplies, such as switch mode power supplies or DC power converters, for providing controlled electrical power to loads. For example, the power supplies may provide different supply voltages to various electrical circuits on a circuit card on which the power supply controller is also provided.
In such a power supply controller, separate IC (integrated circuit) control units can be provided on the primary and secondary sides of a transformer that serves to maintain an electrical isolation barrier between input and output sides of the isolating power supplies. The transformer conveniently provides for signal coupling in both directions between the primary and secondary control units, and also for power transfer from its primary to its secondary side to supply operating power to the secondary control unit and any related circuits (for example, a non-volatile memory) of the power supply controller on the secondary side of the transformer.
Such an arrangement provides significant advantages, for example in requiring only a single transformer to provide electrical isolation between the primary and secondary sides while providing desired bidirectional signal coupling as well as supplying power to the secondary control unit. However, it also requires an effective method for reliably establishing the signal coupling, initially supplying power to the secondary control unit on start-up, ensuring on start-up that the control units are operable to control the isolating power supplies before they can supply power to their loads, and maintaining coordinated operating states of the control units despite errors that may occur in the signal coupling or otherwise.
There is a need to meet these requirements.